1. Field of the Invention
The present invention relates to a display device, and more particularly to an active-matrix-type display device.
2. Description of the Related Art
In the active-matrix-type display device, on a surface of a substrate thereof, for example, a plurality of gate signal lines which extend in the x direction and are arranged in parallel in the y direction and a plurality of drain signal lines which extend in the y direction and are arranged in parallel in the x direction are formed, wherein the display device includes pixel regions each of which has a corner portion at each intersecting portion of these signal lines.
Each pixel region includes at least a thin film transistor which is turned on in response to the supply of a signal (scanning signal) from the gate signal line, and an electrode to which a signal (video signal) is supplied from the drain signal line through the thin film transistor.
This electrode, for example, constitutes one-side electrode which generates an electric field in the inside of liquid crystal in case of a liquid crystal display device, and constitutes an electrode which operates a drive switch element for allowing an electric current to flow into an organic EL element in case of an organic EL display device.
In the display device having such a constitution, by sequentially supplying the scanning signal to the respective gate signal lines from an upper stage to a lower stage, for example, the video signal is supplied to the respective drain signal lines in conformity with the sequential-supply timing of the scanning signal.
Due to such a constitution, through the thin film transistors which are turned on for every pixel row of each stage, the video signal is supplied to the electrodes of the respective pixels of the pixel row.
Further, as the above-mentioned scanning signal which serves to turn on the thin film transistors, usually, a square wave signal is used. That is, the square wave signal is formed of a pulse which rises from a reference potential (low level), holds a fixed voltage (high level) and, thereafter, falls to the reference potential.
However, the scanning signal is not limited to such a square wave signal, and there has been known a wave signal whose waveform is modified as disclosed in a following patent document 1, for example.
That is, the scanning signal disclosed in JP-A-2001-125069 (patent document 1) does not use a square pulse but uses a pulse in which a fixed voltage (high level) is held and, thereafter, the voltage is continuously lowered along with a lapse of time and, thereafter, falls to a reference potential (low level). With the use of such a scanning signal, the irregularities of brightness attributed to a delay of signal due to a gate signal line can be suppressed.